In regions of high evaporation and seasonal rainfall water loss from large open storages due to evaporation is high and is difficult to control.
Evaporation control in relatively small areas of a few hectares or less is usually achieved with a cover over the total surface and anchored at the edges. Australian Patent Application No. 198429445 discloses a water evaporation suppression blanket comprising of interconnected buoyant segments cut from tyres cut orthogonal to the axis of the tyre and assembled in parallel or staggered array.
Australian Patent Application No. 199964460 discloses a modular floating cover to prevent loss of water from large water storages through the natural process of evaporation. Comprising of modular units joined together by straps or ties, manufactured from impermeable polypropylene multi-filament, material welded together to form a sheet with sleeves. The sleeves are filled with polystyrene or polyurethane floatation devices to provide flotation and stiffness to the covers. Australian Patent Application No. 200131305 discloses a floating cover with a floating grid anchored to the perimeter walls of the reservoir, and floating over the liquid level inside the reservoir. A flexible impermeable membrane is affixed to the perimeter walls and is loosely laid over the floating grid.
International Patent WO 02/086258 discloses a laminated cover for the reduction of the rate of evaporation of a body of water, the cover comprising of at least one layer of material that is relatively heat reflecting, and a one second layer of material that is relatively light absorbing.
These prior art devices are restricted to coverage of limited areas by their inherent:                Dynamic inflexibility on the water surface        The need for a fixing mechanism between the modules and/or affixing to the perimeter of the water storage        The need to be anchored and held down during high winds.        
International Patent WO 98/12392 discloses a modular cover for large areas consisting of flat polygonal floating body where the faces of the floating body have partly submerged vertical walls with lateral edges. The device has an arched cover with a hole in the top cover for air exchange. Although the wall depth is large under wave and local high surface wind conditions the covers can be blown off the water surface and overturned.
There is a need for a modular device, which can be easily laid onto large or small water surface areas that will be stable in high wind and wave conditions and remain stable.